Laminated film

Abstract

A laminated film comprising (A) an aromatic polyester film; and (B) a hydrophilic coating layer which is present on at least one side of the aromatic polyester film (A) and has a surface energy of at least 54 dyne/cm, the coating layer comprising (a) 50 to 80% by weight of a copolyester which contains a dicarboxylic acid component having a sulfonate group in an amount of 1 to 16 mol % of the total of all dicarboxylic acid components and has a secondary transition point of 20 to 90° C., (b) 10 to 30% by weight of poly(alkylene oxide) homopolymer having a number average molecular weight of 600 to 2,000, and (c) 3 to 25% by weight of fine particles having an average particle diameter of 20 to 80 nm, based on the total of components (a), (b) and (c). The above laminated film is useful as a transparency for an overhead projector and a recording paper for an ink jet printer.

What is claimed is: 
     
       1. A laminated film comprising: (A) an aromatic polyester film; and   (B) a hydrophilic coating layer which is present on at least one side of the aromatic polyester film (A) and has a surface energy of at least 54 dyne/cm, the coating layer comprising: (a) 50 to 80% by weight, based on the total of components (a), (b) and (c), of a copolyester which contains a dicarboxylic acid component having a sulfonate group in an amount of 1 to 16 mol % of the total of all dicarboxylic acid components and has a secondary transition point of 20 to 90° C.,   (b) 10 to 30% by weight, based on the total of components (a), (b) and (c), of poly (alkylene oxide) homopolymer having a number average molecular weight of 600 to 2,000, and   (c) 3 to 25% by weight, based on the total of components (a), (b) and (c), of fine particles having an average particle diameter of 20 to 80 nm;   wherein the composition comprising:   (a) 50% to 80% by weight, based on the total of components (a), (b) and (c), of a copolyester which contains a dicarboxylic acid component having a sulfonate group in an amount of 1 to 16 mol % of the total of all dicarboxylic acid components and has a secondary transition point of 20 to 90° C.,   (b) 10 to 30% by weight, based on the total of components (a), (b) and (c), or poly (alkylene oxide) homopolymer having a number average molecular weight of 600 to 2,000, and   (c) 3 to 25% by weight, based on the total of components (a), (b) and (c), of fine particles having an average particle diameter of 20 to 80 nm, and produced by a process comprising admixing said components (a), (b) and (c), has a surface energy of at least 54 dyne/cm.     
     
     
       2. The laminated film of claim 1, wherein the dicarboxylic acid component having a sulfonate group contained in the copolyester (a) of the hydrophilic coating layer is an alkali metal salt of 5-sulfoisophthalic acid. 
     
     
       3. The laminated film of claim 2, wherein the alkali metal salt of 5-sulfoisophthalic acid is a lithium salt, sodium salt or potassium salt. 
     
     
       4. The laminated film of claim 1, wherein the proportion of the dicarboxylic acid component having a sulfonate group is 1.5 to 14 mol % of the total of all dicarboxylic acid components. 
     
     
       5. The laminated film of claim 1, wherein the poly(alkylene oxide) (b) of the hydrophilic coating layer is poly(ethylene oxide). 
     
     
       6. The laminated film of claim 1, wherein the fine particles (c) contained in the hydrophilic coating layer are crosslinked organic polymer fine particles. 
     
     
       7. The laminated film of claim 1, wherein the hydrophilic coating layer has a surface energy of at least 60 dyne/cm. 
     
     
       8. The laminated film of claim 1, wherein the aromatic polyester film (A) is a biaxially oriented film which exhibits a thermal shrinkage of 1% or less when it is heated at 150° C. for 30 minutes. 
     
     
       9. The laminated film of claim 8, wherein the aromatic polyester film (A) is a polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate film. 
     
     
       10. The laminated film of claim 1, wherein the aromatic polyester film (A) has a light transmission rate of at least 85% and a haze value of 10% or less. 
     
     
       11. The laminated film of claim 10, wherein the aromatic polyester film (A) has a center line average surface roughness Ra of 5 to 15 nm. 
     
     
       12. The laminated film of claim 1, wherein the aromatic polyester film (A) has a light transmission rate of at least 85% and a haze value of 10% or less, and an aqueous ink-receiving layer is further formed on the hydrophilic coating layer. 
     
     
       13. The laminated film of claim 12 which is a transparency for an overhead projector. 
     
     
       14. The laminated film of claim 1, wherein the aromatic polyester film (A) has a light transmission rate of 20% or less and is white. 
     
     
       15. The laminated film of claim 1, wherein the aromatic polyester film (A) has a center line average surface roughness Ra of 100 to 250 nm. 
     
     
       16. The laminated film of claim 1, wherein the aromatic polyester film (A) has a light transmission rate of 20% or less and is white, and an aqueous ink-receiving layer is further formed on the hydrophilic coating layer. 
     
     
       17. The laminated film of claim 16 which is recording paper for an ink jet printer.